/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.apache.predictionio.data.store

import org.apache.predictionio.data.storage.Storage
import scala.collection.mutable
import grizzled.slf4j.Logger

private[predictionio] object Common {

  @transient lazy val logger = Logger[this.type]
  @transient lazy private val appsDb = Storage.getMetaDataApps()
  @transient lazy private val channelsDb = Storage.getMetaDataChannels()
  // Memoize app & channel name-to-ID resolution to avoid excessive storage IO
  @transient lazy val appNameToIdCache =
    mutable.Map[(String, Option[String]), (Int, Option[Int])]()

  /* throw exception if invalid app name or channel name */
  def appNameToId(appName: String, channelName: Option[String]): (Int, Option[Int]) = {
    appNameToIdCache.getOrElseUpdate((appName, channelName), {
      val appOpt = appsDb.getByName(appName)

      appOpt.map { app =>
        val channelMap: Map[String, Int] = channelsDb.getByAppid(app.id)
          .map(c => (c.name, c.id)).toMap

        val channelId: Option[Int] = channelName.map { ch =>
          if (channelMap.contains(ch)) {
            channelMap(ch)
          } else {
            logger.error(s"Invalid channel name ${ch}.")
            throw new IllegalArgumentException(s"Invalid channel name ${ch}.")
          }
        }

        appNameToIdCache((appName, channelName)) = (app.id, channelId)
        (app.id, channelId)
      }.getOrElse {
        logger.error(s"Invalid app name ${appName}")
        throw new IllegalArgumentException(s"Invalid app name ${appName}")
      }
    })
  }
}
